hey, how do i set my edelbrock 750cfm, i when i got it i just bolted it on, and seemed to work ok, sometimes i get a little black smoke, but i was wondering if i should set the jets or anything because a buddy of mine screwed around with the front 2 screws thinking they were the idle screw, what a **** eh?

anyway is there a link? or do i just give you what kind of motor im running? its in my signature...

 

The stock jetting that comes in a 750cfm edelbrock will work very well in your combo.
Unless you going to the track to get timed runs to compare changes, its hard to improve on it.
The idle mixture screws adjust just like any other carb. use a vacuum guage and with the motor completely warmed up to operating temp. ( 15-20 minutes of running) adjust the idle mixture screws for best idle quality and manifold vacuum. adjust them slowly and evenly.
Unlike EFI:
With the motor set up warm, its normal for it to run rough and (may) want to stall, when the motor is first started, until it fully warms up. The engine heat helps vapourise the fuel in the manifold.

Until the motor fully warms up :
The choke and fast idle system is used to help the motor run
until it gets some heat in the intake manifold.
Hook up the choke and use it for cold starting and warm up. Get used to it.

Edelbrock carb tuning

 

yes, it has an electric choke that works great.

ok so can u just tell me real quick which way do i turn to increase the 2, and which way decreases the mixture.

thanks.

 

The two screws on the front of the carb control the idle mixture. Turning them in- clockwise, leans the idle mixture.
Turning them out- counter clockwise makes the idle mixture richer. Black smoke indicates an ignition problem. Make sure the engine is physically electrically grounded to the fire wall on a third gen. Makes a difference.
Exactly which cam do you have?

 

ok well how will i know what is too rich or lean, just listen to the idle? i have the idle around 700rpm from the idle screw myself, and set the timing to 12

a peanut cam

the crane energizer 10052 .454 lift 216 duration

 

get the motor warmed up. Turn each screw, one at a time , slowly in(clockwise) until the motor just starts to slow down. Then turn that screw out (counterclockwise) , until the motor just recovers. Repeat the adjustment for the other screw.

Correct mixture is right at the point where the motor just recovers after first turning each screw in ( idle rpm will just drop) and then out again (idle speed just recovers.) A vacuum guage helps but you can adjust it properly by ear. 12degrees initial at idle sounds fine for your setup. How much total mechanical advance do you have. (vacuum disconected) At high rpm?

 

umm i have vacuum advance, and it will be plugged in, but i dont know how to set the mechanical or vacuum advance, any help?

 

Well to set-up the mechanical advance, disconnect the vacuum advance, loosen the distributer to where you can just turn it, mark the balancer with the tape, or measure the OD of the balancer and divide it by 10. That will give you a measurement to determine where 36* total timing is. Mark the damper 36* in front of the timing mark (counter-clockwise from the mark). White-out works well. The next part works better with two people. Connect a tach, start the engine, let it warm up , the next part may sound a little weird, but bring the engine slowly up to 3,500-4,000 rpm, watching the advance come up, eventually it will stop climbing, take note of the RPM, now adjust the timing for 36* total. Let the engine return to an idle, now take note of the initial advance it will probably be about 12-14*. Take note of this. Now you now where 36* total advance is. You want about 32-36* of total timing at about 2,800-3,200 RPM and as much initial as you can get away with. Listen for engine ping.

Vacuum advnace is alot simpler. Bolt an adjustable vacuum advance on it, with the total timing at 36* and initial around 12* you want about 10* of vacuum advance at about 10 in/hg of vacuum. Depending on the engine combo it will take more or less. Connect the vacuum advance to manifold vacuum.

 

The mechanical advance is checked with a timing light with the vacuum advance hose temperairly disconnected.
Should be 12 to 18deg at idle (700rpm). Should advance smoothly to 32-36deg at high rpm. Should reach full advance @ 3000-3500rpm. {32-36deg}
It's mechanical travel is adjusted by using different advance travel limiting bushings. Its rate of advance is ajusted by different mechanical advance springs ( tension).
Vacuum advance is separate issue. Setup the mechanical advance first.
Use ported vacuum.
Vacuum advance is employed while cruising on the hwyway.
Vacuum advance amount is adjusted by the length of travel of the rod that connectes the vacuum advance diaphram to the distributor. (underside of advance)
vacuum "rate of advance" ( how much ,how fast is adjusted by the tension on the diaphran spring inside the vacuum advance housing). You can select different "stock" advance housings or get a Crane adjustable one. Your proform distributor should have an adjustable one.
Should have come with a allen key and a limiting plate to set up the vacuum advance.

While cruising down the hiway @100 K/PH, in D2 (second gear) ( not OD) you want a total mechanical and vacuum advance combination of 51 degrees maximum.
Note** The engine rpm@speed must be high enough to max out the distributor advance. use "D2"

Eg: If you have 36deg mechanical at 3000rpm you need a max of 15 degrees vacuum advance.
36+15=51 The best rate of advance (spring tension) needs to be found by trial and error. Too much will cause pinging when you roll into the throttle.

You need to establish the maximum "cruising manifold vacuum and RPM" . You can do this by hooking up a vacuum guage inside the car temperairly and go for ride. In second gear, try driving along at different steady speeds. (should be above 3000-3500rpm) Find out the maximum vacuum guage reading point at a steady driving speed. This "Steady Speed *MAX* Vacuum Reading" is the vacuum point that you need 51 degrees. Remember this max vacuum reading and engine RPM. Set up the distributor to have total *combined* M an V advance of 51 deg maximum at this rpm and manifold vacuum point. From this point you only need to experiment with the rate of vaccuum advance (spring tension) (Trial and error) too much (too light a diaphram spring tension) will cause pinging and or surging.

The driving speed you'll be using to find this vacuum/rpm
test point will be 70 to 110KPH {depends on your rear gear ratio} while in "D2" second gear. Use second gear to find the high point to ensure the engine rpm @ cruising speed is high enough to max out the distributor advance. 3000+engine RPM
You can then use a mechanics vacuum pump to set up the distributor for 15deg travel @ the manifold vacuum point you established during the drive test.

This agressive max performance ignition timing curve will probabily require premium pump gas (92+octane). even with a low compression ratio . If it is just too agressive just back off on the 51deg total a little to suite your car and octane preference. (a little less than 51deg total)

 

f-bird you get pretty technical!! both thanks alot for your help

i understand, but not completely, so i wont touch it until i fully know what im doing.

what i get is, after TDC 1 with timing set at 12, i loosen the distributor, and now i mark a white line behind (counter clockwise) from my timing mark at 36 degrees, do i leave the balancer in the position it is or bring the 36 degree mark mark to TDC? then i start the car, ill have my brother sit in the car bring up the rpm's up to 3.5-4k, then watch the advance go up to 36, when it stops climbing i set the timing, i set the timing to 36 while im doing this? will it affect timing at idle when it was at 12?

 

Actually I made a mistake, advance is clockwise as it is advance or before the mark with the engine rotating clockwise. Long day! You want to know the diameter of the balancer so that you can find out what 36 degrees is. 36 degrees is a typical number for a small block chevy with conventional heads on it. You want to know where a total of 36* advance is, the mechanical advance won't advance until you rev the engine up. You reach your total advance whenever it stops climbing. When it stops climbing, around 4K RPMs, that is when you adjust the timing to line up with the mark you made on the balancer.

By knowing the diameter and that the balancer is 360* it is pretty simple to get the diameter you need. Simply take the measurement and divide by 10. Take a piece of paper and cut it to that length, now mark the balancer. You now have 36* total. By setting the timing to 36* total you will change the Initial or Base timing. The centrifical advance will typically have 20-24* advance @ 3,500-4,000 on a stock type distributer. That gives you a range of 12-16* initial.

 

If you end up with more than 12degrees at idle, once you set up the total mechanical timing at high engine rpm to 36deg, thats ok. 12 to 18deg at idle advancing to 32-36deg at high rpm is right for the mechanical curve.
it is easier to do with a balancer timing tape (Mr gasket) or a advance timing light.

You need to know where TDC is where 36degrees is and where 51degreees is.
36degrees is the maximum mechanical timing point.
51deg is the maximun *combined* timing point while cruising down the road at *max vacuum/RPM point*)

got you confused yet.... LOL

 

Exactly. Except I use 51* with EGR and 45* without.

Timing tape makes it alot easier, but it is not always easily available. I tried several places, before I just thought about doing it my way.

I think we have him confused.

 

ok so im looking at the motor front nose cone, im looking at the balancer at the timing mark is top dead center, i mark the mechanical advance 36 degress to the RIGHT of the timing mark, correct.

once i do that i fire up the motor, get my brother to rev the motor slowly, and me with the timing gun shining at the new mark i get him to rev i up and i watch it as it climbs, and once it stops climbing i move the turn the distributor, to where, turn the distributor until the timing light lines up with the new mark?

im less confused then i was, but you guys are helping alot, im learning better...

 

Looking at it from the front, you mark it to the right or clockwise as that is the direction the engine is turning (have been looking at my boat recently as well).

When it stops advancing, move the distributer until the timing light matches up with the new mark. Just don't keep the engine singing at high RPM very long and don't push it much above 4,000.

If it is still advancing at 4,000 rpm it is time for some lighter advance springs.

Make sure to chock the wheels and set the parking brake, I would hate to see you pinned against a garage door or something.

 

ok so im gonna keep the light at 36 degrees and turn the distributor until it lines up with the mark.

i think i got it

 

You'll be able to visualise what I typed much better once you get in there with the timing light hooked up and the engine running and watch how the timing point moves as you rev the engine.

Should not exceed36deg while reved up to about 3500-4000rpm with vacuum advance disconnected

And should not exceed 51deg while reved up with the vacuum advance connected.

To find out exactly how much mechanical max timing your motor wants to develop max power requires a dyno test session or a day at Cayuga testing different timing points that give *best MPH* on the time slip. but will be between 32 and 36deg. Anything much beyond these benchmarks indicates
a wacked out balancer or too lean/ too rich jetting.
Your carb will be very close to best as is with stock jetting though. Optimised best will be only a few jet sizes up or down from that starting point. this cannot be found by seat of the pants testing (the butt dyno) or in the driveway.

You need to spend a day "test and tuning" at the track
bring a box of jets and metering rods and a timing light.

 

yes i plan on going there in the spring for test and tune.

thanks alot, i will try this tomorrow and get back to you what happens, i will probably screw something up haha

 

The critical setting for a Edelbrock carb are the fuel pressure
5-6PSi and the carb float height setting. too high and the car will stumble while going around sharp corners. Too low and the engine will starve at WOT. I run mine just a little lower setting than the standard setting.

Edelbrock carbs tend to run too hot in the summer (heat soak.) A wooden divided carb spacer/isolater is nice to control the fuel bowl temp. A small under hood fan to blow air on the carb helps also if you get exessive heat soak on really hot days.

 

i have a spacer, a polished one, or chrome i forgete i havent looked at it in a while, i just need to get some bolts that are longer.

so i should use the spacer, im just wondering if i will have clearance with the air gap, 1" spacer, carb, and 14" air breather.

 

Shiny things don't make the car go faster.
Polish it up and sell it to some one else. You want a spacer made out of WOOD!!! Wood is an excelent heat isolator.
for a dual plane manifold you want a divided spacer. Or a 4hole spacer. Edelbrock sells WOODEN carb spacers or you can make your own, out of WOOD!!!....DID I mention the WOOD???

Doesn't have to be 1" thick. 1/4" to 1/2" should do it.
Search my posts on fitting it all under a stock hood.

Use the Search word : L-88
Do you have a mechanical fuel pump?

 

hold'r now, i didnt say shiny things go faster, im tellin what i have, a 4 hole spacer, its either chrome or polished aluminum.

i didnt mean to say i dont want wood, but that its what i had, but thanks, ill look into the wood. did i meantion ill look for a wood one? HAHA just kidding.

yeah its a mechanical fuel pump, just put a new one in, 20$ from crappy tire

 

Just giving ya a hard time

Here is a trick little fuel pump gasket/ heat isolator with special mounting bolts that keeps the fuel pump from soaking up so much heat (vapour lock) Even keeps the hot engine oil off the back of the pump.

fuel pump mounting heat isolator CTC can order one in for ya.

 

this isnt about the carburetor

but with the pushrods i was checking, if it looks right but when u use the pushrod checker, what if when u put the rocker arm on and when u slide it over the rocker stud it sits on the valve tip(spring) before it touches the pushrod just by like 1 second, haha, does that make a difference, im not sure since the valve tips are on an angle.

 

rough,

With your RPM Airgap and Twisted heads I was curious as to how well your setup ran in winter. But since you garage it you'll be okay. Otherwise your engine might never warm up enough to make your carb happy and idle right. Your heads and intake don't have the heat crossover that runs under the carb to get things up to temp.

It's a problem I have with my Performer carb, even though my heads and intake are equipped with the heat crossover. It is hard to get the second stage of the choke to let go, so the engine can idle at 650 rpm or so when I'm in traffic. Or it will idle correctly but then the low stage of the choke comes back on due to the cold air rushing under the hood when it is -10 or -20 or so. It's a real pain and I wish it would sort itself out

 

really well i havent had it running yet since it starting getting really cold out, i will get my new pushrods on monday and i will have it back together and fired up, and i will see how the setup works.